Physics 9702/33 February/March 2021: question paper and mark scheme
Cambridge AS & A Level Physics (9702), Paper 3 Advanced Practical Skills 1, February/March 2021. Read both free below, or download them. Done the paper? Get it marked by AI against this mark scheme.
In this experiment, you will investigate the equilibrium of a wooden rod supported by a spring.
(a) (i) Before assembling the apparatus, measure and record the length Co of the coiled section of the spring, as shown in Fig. 1.1.
Co string loop
spring string
Fig. 1.1
Co = …… cm [1]
(ii) • Assemble the apparatus as shown in Fig. 1.2 with each nail held securely in a boss.
stand upper nail
boss string
clamp C string loop holding split cork spring wooden rod bosses grooves
lower nail x
bench
Fig. 1.2
• Adjust the bosses until the upper nail is approximately 35 cm above the bench and the lower nail is approximately 10 cm above the bench.
• Position the string loop in one of the grooves near the middle of the rod.
• Adjust the free end of the string so that the rod is parallel to the bench and then secure it in the split cork.
• Measure and record the length C of the coiled section of the spring, as shown in
Fig. 1.2.
C = …… cm
• Calculate E, where E = C − Co.
E = …… cm
[1]
(iii) The distance from the centre of the lower nail to the groove with the string loop in it is x.
Measure and record x.
x = …… cm [1]
(b) Move the string loop into another groove and adjust the apparatus so that the rod is parallel to the bench.
Measure C and x.
Repeat until you have at least six sets of values of C and x.
1
Record your results in a table. Include values of E and 4 in your table.
E
[9]
1
(c) (i) Plot a graph of on the y-axis against x on the x-axis. [3]
E4
(ii) Draw the straight line of best fit. [1]
(iii) Determine the gradient and y-intercept of this line.
gradient = ……
y-intercept = ……
[2]
(d) It is suggested that the quantities E and x are related by the equation
1
= ax + b
E4 where a and b are constants.
Use your answers in (c)(iii) to determine the values of a and b.
Give appropriate units.
a = ……
b = ……
[2]
[Total: 20]
You may not need to use all of the materials provided.
Mark scheme
1(a)(i) Value of Co to the nearest mm and in range 1.5 cm to 3.0 cm 1
1(a)(ii) Value of C > Co 1
1(a)(iii) Value of x in range 14.0 to 33.0 cm 1
1(b) Six sets of readings of C and x with correct trend and without help scores 4 marks, five sets scores 3 marks etc. 4
Range: 1
xmax - xmin ⩾ 14.0 cm
Column headings: 1
Each column heading must contain a quantity and a unit where appropriate.
The presentation of quantity and unit must conform to accepted scientific convention e.g. 1 / E4 / cm–4
Consistency: 1
All values of raw x must be given to the nearest mm
Significant figures: 1
Values of 1 / E4 should be to the same s.f. (or one more than) the s.f. in the corresponding value of E.
Calculation: 1
Values of 1 / E4 calculated correctly
1(c)(i) Axes: 1
Sensible scales must be used, no awkward scales (e.g. 3:10)
Scales must be chosen so that the plotted points occupy at least half the graph grid in both x and y directions
Scales must be labelled with the quantity which is being plotted.
Scale markings should be no more than 3 large squares apart.
Plotting of points: 1
All observations must be plotted on the grid.
Diameter of plotted points must be ⩽ half a small square (no blobs).
Plots must be accurate to within half a small square in both x and y directions.
Quality: 1
All points in the table must be plotted (at least 5) for this mark to be awarded. Scatter of plots must be no more than ±
2.0 cm (to scale) from a straight line in the x direction.
1(c)(ii) Line of best fit: 1
Judged by balance of all points on the grid (at least 5) about the candidate’s line. There must be an even distribution of
points either side of the line along the full length
One anomalous point is allowed only if clearly indicated (i.e. circled or labelled) by the candidate.
Lines must not be kinked or thicker than half a square.
1(c)(iii) Gradient: 1
The hypotenuse of the triangle used must be greater than half the length of the drawn line.
Method of calculation must be correct.
Both read-offs must be accurate to half a small square in both the x and y directions.
y-intercept: 1
Either
Correct read-off from a point on the line substituted into y = mx + c or an equivalent expression, with read-off accurate to
half a small square in both x and y directions.
Or
Intercept read directly from the graph, with read-off at x = zero accurate to half a small square in y direction.
1(d) a equal to candidate’s gradient, and b equal to candidate’s intercept. Values are not written as fractions. 1
Unit for a is dimensionally correct, e.g. cm–5 1
and unit for b is dimensionally correct, e.g. cm–4
In this experiment, you will investigate the speed of air flowing through a hole.
(a) • You are provided with a plastic bottle with the base cut off. The neck is sealed with a polythene sheet. Two lines are marked on the side of the bottle, as shown in Fig. 2.1.
polythene sheet
rubber band
upper line
lower line
bottle
Fig. 2.1
The distance between the lines is L, and the diameter of the bottle where the lines are marked is D, as shown in Fig. 2.2.
bottle
L
D
Fig. 2.2
• Measure and record L and D.
L = …… cm
D = …… cm
[2]
(b) (i) You have been provided with a pin and a thin nail.
• Make a hole through the polythene sheet using the pin, as shown in Fig. 2.3.
make hole here
pin
Fig. 2.3
• Measure and record the diameter d of the pin.
d = …… cm [1]
(ii) Estimate the percentage uncertainty in your value of d.
Show your working.
percentage uncertainty = …… [1]
(c) • Submerge the bottle in the bowl so that it is completely filled with water.
• Tilt the bottle until it is vertical with its lower end approximately 1 cm below the water level in the bowl, as shown in Fig. 2.4.
upper line
bowl lower line water
� 1 cm
Fig. 2.4
• The water level in the bottle will fall.
Start the stopwatch when the water level reaches the upper line, and stop the stopwatch when the water level reaches the lower line.
Record the time t shown on the stopwatch.
t = …… [2]
(d) • Remove the bottle from the bowl.
• Push the nail through the pin-hole in the polythene to make the hole larger.
• Measure and record the diameter d of the nail.
d = …… cm
• Repeat (c).
t = ……
[2]
(e) It is suggested that the relationship between t and d is k t= d2 where k is a constant.
(i) Using your data, calculate two values of k.
first value of k = ……
second value of k = ……
[1]
(ii) Justify the number of significant figures you have given for your second value of k.
…… [1]
(iii) Explain whether your results support the suggested relationship.
…… [1]
(f) The speed S of the air passing through a hole is given by
D 2L
S= . k
Calculate S using your second value of k.
S = …… [1]
(g) (i) Describe four sources of uncertainty or limitations of the procedure for this experiment.
1 ……
2 ……
3 ……
4 ……
[4]
(ii) Describe four improvements that could be made to this experiment. You may suggest the use of other apparatus or different procedures.
1 ……
2 ……
3 ……
4 ……
[4]
[Total: 20]
Mark scheme
2(a) Value of L in range 2.5 cm to 3.5 cm and given to nearest mm or better 1
Value of D in range 6.0 to 9.0 cm and given to nearest mm or better 1
2(b)(i) Value of raw d to nearest 0.001 cm and final value in range 0.040 cm to 0.090 cm 1
2(b)(ii) Absolute uncertainty of 0.001 cm and correct method of calculation to obtain percentage uncertainty in d. 1
If several readings have been taken, then the absolute uncertainty can be half the range, but not zero if values are equal.
2(c) Value for t in s, with unit 1
Evidence of repeat readings for t 1
2(d) Second values for d and t 1
Quality: second t shorter than first t 1
2(e)(i) Two values of k calculated correctly. 1
2(e)(ii) Justification based on sig. fig. in t and d 1
2(e)(iii) Sensible comment relating to the calculated values of k, testing against a criterion specified by the candidate. 1
2(f) Correct calculation of S 1
2(g)(i) Two k values are not enough to draw a valid conclusion 4
Hole may not be same size as pin
Difficult to measure D as bottle distorts
Difficulty with 1 cm depth with reason, e.g. holding bottle steady (when timing) / seeing what the depth is
Difficulty with measuring time with reason, e.g. lines are thick / difficult to judge when level passes line / difficult to see
water level
4 max
2(g)(ii) Take more readings and plot a graph / calculate more k values and compare 4
Measure hole itself, with detail of method
Stand bottle on graph grid / use a more rigid named material for bottle / measure with bottle between blocks
Place bottle on a support in the bowl / clamp bottle (after filling) / mark line 1 cm from bottom of bottle
Video with timer in view (or frame by frame) / use coloured water
4 max
Checked your answers against these? Let AI mark the whole paper, on your own working.
Examiners follow the generic marking principles at the front of the scheme, then each question's points: method (M), accuracy (A) and independent (B) marks, error carried forward where the scheme allows it, and positive marking, so you're credited for what you got right.
Check your answers against it
Done this paper? Upload your script and CIE Buddy's AI marker marks it question by question against this exact scheme, puts the ticks on your own working and says what each lost mark needed.
Where can I find the 9702/33 February/March 2021 mark scheme?+
On this page, free: the mark scheme for AS & A Level Physics 9702/33, February/March 2021 (9702_m21_ms_33), and the question paper (9702_m21_qp_33), to read or download, with each question's marking points written out underneath.
How many marks is 9702/33 out of?+
Physics 9702/33 for February/March 2021 is out of 40 marks, with 2 hours to answer it, across 2 questions.
Can I get my 9702/33 answers marked?+
Yes. Upload your answers to 9702/33/F/M/21 as a PDF or photos, and CIE Buddy marks every question against this paper's official mark scheme, using Cambridge's marking rules. You get your score, each lost mark explained on your own script, and the topics to revise. It's a guide, not an official Cambridge grade.